1. Field of the Invention
The invention relates to a wind turbine bearing arrangement that is designed as a main bearing for a rotor of the wind turbine, as well as a method for adjusting a preload of a bearing arrangement of the type specified.
2. Description of the Background Art
Wind turbines generally feature a turbine, at the front end of which is arranged a rotatable gondola which constitutes a machine carrier. On the gondola, a rotor hub is mounted rotatably around a rotational axis, with rotor blades being secured to the hub. Wind turbines can either employ a direct drive concept, according to which the rotational motion of the rotor hub is directly and immediately transmitted to a rotor of a generator, or have gearing interposed between the rotor hub and the generator.
One of the technical challenges with wind turbines of this type, which are typically designed for electrical output ranging in the several MW, is providing a bearing that can satisfy the high technological demands, such as high flexural stiffness, play-free bearing, low-wear kinematics as well as being as simple as possible to assembly while offering high efficiency at the same time. When operating, modern wind turbines are subjected to a host of load fluctuations and environmental influences which considerably impact the strain on and function of all components. These fluctuations can lead to component overload and damage and thereby high consequential expenses. To prevent this, individual components are normally overdimensioned to safeguard against all possible fluctuations in load. This problem is likewise seen in what is referred to as the main bearing of the wind turbine, which constitutes the linking member between the rotating system and the stationary system. All load fluctuations which result from the site of the installation, from malfunctions in pitch or azimuth systems or from control fluctuations of electrical network, generator and converter, must be absorbed by this main bearing. This results in a conservative and thus a not especially dimensioning of the main bearing. In addition to these economic aspects, this type of overdimensioning results in an increased frictional torque compared to that of a normal design, which in turn results in shorter service lives, increased breakaway torque at low wind velocities and increased strain on materials and construction elements.